It is known from WO 01/54450 to couple a DMA to a site to which force is to be applied by an off-centre coupling means, e.g. a stub. Furthermore, it is known from WO 01/54450 that the parameters of the DMA may be adjusted to enhance the modality of the DMA.
It would be desirable to provide an alternative method for changing the fundamental resonance of the transducer.